1. Field
The following description relates to a radio frequency identification (RFID) technology, and more particularly, to an RFID sensor tag.
2. Description of the Related Art
A radio frequency identification (RFID) technology is a technology that allows pieces of information to be read out from RFID tags applied to products or objects over a short distance by use of radio frequencies. A tag to be applied to a product contains all kinds of information on production, distribution and customer. Therefore, through the RFID tag, the information can be transferred to other information systems. An RFID system comprises of an RFID tag for storing information and for exchanging information through a wireless protocol and an RFID reader for RF communication with the RFID tag. There are generally two types of RFID tags, active RFID tags and passive RFID tags, depending on whether a self-power supply is present. The active RFID tags contain a battery and operate autonomously and the passive RFID tags have no battery and extract power components from contiguous electromagnetic waves output from the RFID reader and received through an antenna to generate power. The active RFID tags have advantages in reducing the required power of an appropriate RFID reader and having an increased recognition distance, but have limitations in price and application since the RFID tags include a power supply. On the other hand, the passive RFID tags are inexpensive and can be used semi-permanently, but have a shorter recognition distance, make the RFID reader use more power and cannot store as much data as the active RFID tags can.
With the expansion in use of the RFID tags in various fields of technology and the diversification of applications, functions of the RFID tags have become more varied. In particular, the amount of data to be stored in an RFID tag for simple product management may be only several bytes, but a sensor tag such as a ubiquitous sensor network (USN) may store data of several thousand bytes. In the storing of data sensed via a sensor, the sensor tag can enhance the efficiency of the sensor and more appropriately function as the amount of data to be stored in a memory space increases.
However, as the amount of data to be stored in the sensor tag increases, the capacity of a memory becomes larger, resulting in an increase in power consumption. If the power consumption increases, a passive sensor tag cannot be used. Moreover, even if the sensor tag is of an active type, the lifetime of a battery is shortened, causing various limitations in use. Especially, since the memory of an RFID tag is generally non-volatile, processes of erasing current data and writing a value of new data have to be performed in order to write the new data. Furthermore, since a high voltage is required for the processes, the total power consumption may be increased.